Material and method of manufacturing of a solder joint with high thermal conductivity and high electrical conductivity

ABSTRACT

A solder composition for forming a solder joint. The composition includes a powder material including a solid metal matrix material and a filler material. The solid metal matrix material includes one or more of tin-silver-copper (Sn—Ag—Cu), tin-copper (Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag), tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold (Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi), tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium (In), indium-silver (In—Ag), and tin-lead (Sn—Pb). The filler material includes one or more of copper (Cu), gold (Au), nickel (Ni), nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum (Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinum group metals (PGM&#39;s), and their alloys.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 11/598,062 filed Nov. 13, 2006, now U.S. Pat. No.7,758,916, the disclosure of which is expressly incorporated byreference herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

REFERENCE TO A “MICROFICHE APPENDIX”

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of materialstechnology and more particularly to a solder composition having improvedthermal and electrical properties and a method for manufacturing thesame.

2. Description of the Related Art

In any circuit involving electrical power, a major design objective isto reduce the temperature of the components, improve reliability, reducecost, and improve operation. Many integrated circuits (“ICs”)—including,for example, dual in-line plastic packaged ICs—have shapes not conduciveto fastening directly to the chassis. The packaging method for an ICbecomes a limiting factor, as the package serves the function ofcarrying high current densities in addition to high thermal loads.

In some cases, the design limit of the package becomes the interfacesbetween the IC and the package, which is itself limited by themanufacturing technique used. A reason for this is that the interfacematerials best suited for good performance are those that posses bothhigh electrical and thermal conductivity (such as copper or gold).However, these material also have melting points well beyond themanufacturing temperatures that can be tolerated for the IC. Thus, lowermelting point solders are typically used to make the interface joint.But these solders do not have an ability to move heat and electrons aswell as the interface materials themselves and thus limit theperformance potential of the package. There remains a need in the artfor a solder joint with improved electrical and thermal conductivity anda melting point low enough to prevent damage to the IC during soldering.

By reducing the thickness of the solder layer, conductive performance isimproved. The thickness of the solder layer is limited by the toleranceof the IC and package in addition to the manufacturing method used.Thus, there remains a need in the art for a solder joint that canprovide minimal solder thickness for IC applications.

SUMMARY

By combining a solder material and high conductivity (thermal andelectrical) material, it is possible to create a composite material thatis both solderable at a low temperature and has increased thermal andelectrical conductivity compared to using solder alone. The presentinvention provides a powder blend or composite powder that is fed into akinetic spray device, accelerated towards a substrate or part in orderto form a composite solder with thermal and electrical properties betterthan conventional solders. The other advantages of building a solderlayer in this manner include a low oxide content to improve subsequentsolderability, excellent control of the deposition thickness, excellentcontrol of the deposition chemistry and lastly, high speed ofmanufacture.

In one aspect of the invention, a powder blend for kinetic spraying isprovided that contains a solder metal matrix with two parts: (1) one ormore of tin-silver-copper (Sn—Ag—Cu), tin-copper (Sn—Cu),tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag), tin -silver-bismuth(Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold (Au—Sn), tin-zinc(Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi), tin-bismuth-silver (Sn—Bi—Ag), tin(Sn), tin-indium (Sn—In), indium (In), indium-silver (In—Ag), andtin-lead (Sn—Pb); and (2) a filler material with high thermal andelectrical conductivity of one or more of copper (Cu), gold (Au), nickel(Ni), nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al),molybdenum (Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, theplatinum group metals (PGM's), and their alloys.

Another aspect of the invention provides a method for manufacturing thepowder blend. The method includes the step of providing a solder metalmatrix material made of one or more of tin-silver-copper (Sn—Ag—Cu),tin-copper (Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag),tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold(Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi),tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium(In), indium-silver (In—Ag), and tin-lead (Sn—Pb)—although Pb has beenlegislated for removal from solders by the European Parliament Directive2002/95/EC on the “Restriction of the Use of Certain HazerdousSubstances in Electrical and Electronic Equipment” (RoHS), which will beadopted worldwide due to the global nature of the electronics industry;and providing a filler material made of one or more of copper (Cu), gold(Au), nickel (Ni), nickel-gold (Ni—Au), carbon, silver (Ag), aluminum(Al), molybdenum (Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon,the platinum group metals (PGM's), and their alloys. The matrix materialand filler metal are then each formed into powder particles. Finally,the solder metal matrix powder particles and the filler metal powderparticles are blended to a desired ratio for spraying.

In another aspect of the invention, composite powder particles forkinetic spraying are provided with an inside component including fillermetal with high thermal and electrical conductivity composed of one ormore of copper (Cu), gold (Au), nickel (Ni), nickel-gold (Ni—Au),carbon, silver (Ag), and molybdenum (Mo); and an outside componentincluding a solder metal matrix composed of one or more oftin-silver-copper (Sn—Ag—Cu), tin-copper (Sn—Cu), tin-copper-nickel(Sn—Cu—Ni), tin-silver (Sn—Ag), tin-silver-bismuth (Sn—Ag—Bi),tin-bismuth-indium (Sn—Bi—In), tin-gold (Au—Sn), tin-zinc (Sn—Zn),tin-zinc-bismuth (Sn—Zn—Bi), tin-bismuth-silver (Sn—Bi—Ag), tin (Sn),tin-indium (Sn—In), indium (In), indium-silver (In—Ag), or tin-lead(Sn—Pb). Alternatively, the inside component may be one or more ofalloys based on aluminum (Al), molybdenum (Mo), copper (Cu), gold (Au),silver (Ag), nickel (Ni) or nickel-gold (Ni—Au) coated carbon (typicallygraphite, diamond or carbon nanotubes—SWNT), or the platinum groupmetals (PGM's).

Yet another aspect of the invention includes methods for manufacturingthe composite powder is also provided. The method of manufactureincludes the step of providing an inside particle component made of afiller metal with high thermal and electrical conductivity, such as oneor more of copper (Cu), gold (Au), nickel (Ni), nickel-gold (Ni—Au),carbon, silver (Ag), molybdenum (Mo), and any alloys thereof. Next, theinside component is formed into powder particles. An outside componentmade of one or more of tin-silver-copper (Sn—Ag—Cu), tin-copper (Sn—Cu),tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag), tin-silver -bismuth(Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold (Au—Sn), tin-zinc(Sn—Zn), tin -zinc-bismuth (Sn—Zn—Bi), tin-bismuth-silver (Sn—Bi—Ag),tin (Sn), tin-indium (Sn—In), indium (In), indium-silver (In—Ag), ortin-lead (Sn—Pb) is provided. And finally, the outside component isdeposited onto the inside component using one or more of electrochemicalmethods, chemical methods, physical vapor deposition (PVD), ormechanical cladding.

In other aspects of the invention, a method of applying composite soldermaterials is provided. The method includes the steps of providing powdermaterials comprising a solid metal matrix material and a filler materialeach in accordance with the material composition described above;supplying the powder materials to a kinetic spraying apparatus; andspraying the powder materials through a convergent-divergent nozzle ontothe substrate at pressure less than or equal to ambient.

In other aspects of the invention, a solder composition for forming asolder joint comprises a powder material including a solid metal matrixmaterial and a filler material. The solid metal matrix materialcomprises one or more of tin-silver-copper (Sn—Ag—Cu), tin -copper(Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag),tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold(Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi),tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium(In), indium -silver (In—Ag), and tin-lead (Sn—Pb). The filler materialcomprises one or more of copper (Cu), gold (Au), nickel (Ni),nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum(Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinumgroup metals (PGM's), and their alloys.

In other aspects of the invention, the solder composition is sprayableonto a substrate via a kinetic spraying apparatus.

In other aspects of the invention, a composite solder coating is formedby spraying the solder composition described above onto a substrate atpressure less than or equal to ambient.

In other aspects of the invention, a solder composition for forming asolder joint comprises a powder material including a solid metal matrixmaterial forming an outer shell surrounding a filler material. The solidmetal matrix material comprises one or more of tin -silver-copper(Sn—Ag—Cu), tin-copper (Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver(Sn—Ag), tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In),tin-gold (Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi),tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium(In), indium-silver (In—Ag), and tin-lead (Sn—Pb). The filler materialcomprises one or more of copper (Cu), gold (Au), nickel (Ni),nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum(Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinumgroup metals (PGM's), and their alloys.

In other aspects of the invention, the solder composition is sprayableonto a substrate via a kinetic spraying apparatus.

In other aspects of the invention, a composite solder coating is formedby spraying the solder composition described above onto a substrate atpressure less than or equal to ambient.

In other aspects of the invention, a solder composition for forming asolder joint comprises first powder particles comprising a solid metalmatrix material and second powder particles comprising a fillermaterial. The solid metal matrix material comprises one or more oftin-silver-copper (Sn—Ag—Cu), tin-copper (Sn—Cu), tin-copper-nickel(Sn—Cu—Ni), tin-silver (Sn—Ag), tin-silver-bismuth (Sn—Ag—Bi),tin-bismuth-indium (Sn—Bi—In), tin-gold (Au—Sn), tin-zinc (Sn—Zn),tin-zinc-bismuth (Sn—Zn—Bi), tin-bismuth-silver (Sn—Bi—Ag), tin (Sn),tin-indium (Sn—In), indium (In), indium-silver (In—Ag), and tin-lead(Sn—Pb). The filler material comprises one or more of copper (Cu), gold(Au), nickel (Ni), nickel-gold (Ni—Au), carbon, silver (Ag), aluminum(Al), molybdenum (Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon,the platinum group metals (PGM's), and their alloys. The soldercomposition comprises a blend of the first and second powder particles.

In other aspects of the invention, the solder composition is sprayableonto a substrate via a kinetic spraying apparatus.

In other aspects of the invention, a composite solder coating is formedby spraying the solder composition described above onto a substrate atpressure less than or equal to ambient.

In other aspects of the invention, a powder composition for forming asolder joint comprises a metal matrix material and a filler material.The metal matrix material comprises one or more of tin-silver-copper(Sn—Ag—Cu), tin-copper (Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver(Sn—Ag), tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In),tin-gold (Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi),tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium(In), indium-silver (In—Ag), and tin-lead (Sn—Pb). The filler materialcomprises one or more of copper (Cu), gold (Au), nickel (Ni),nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum(Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinumgroup metals (PGM's), and their alloys. The powder composition comprisesone of a blend of said metal matrix material and said filler material,composite powder particles comprised of said metal matrix material andsaid filler material, and powder particles each including said metalmatrix material forming an outer shell surrounding said filler material.

In other aspects of the invention, the powder composition is sprayableonto a substrate via a kinetic spraying apparatus.

In other aspects of the invention, a composite solder coating is formedby spraying the powder composition described above onto a substrate atpressure less than or equal to ambient.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide further understandingof the invention and are incorporated in and constitute a part of thisspecification. The accompanying drawings illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention. In the figures:

FIG. 1 is a schematic of a typical kinetic spray system for use with thepresent invention;

FIG. 2 shows a process flow for the method of producing a powder blendin accordance with the present invention;

FIG. 3 is a schematic of a composite powder particle in accordance withan embodiment of the present invention;

FIG. 4 shows a process flow for the method of producing composite powderparticles in accordance with the present invention;

FIG. 5 is a schematic of an applied solder coating prior to soldering inaccordance with an embodiment of the present invention;

FIG. 6 is a schematic of an applied solder coating after soldering inaccordance with an embodiment of the present invention; and

FIG. 7 provides a process flow for producing a solder coating onto asubstrate in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

The composite material of the present invention may be used in a kineticspray system. FIG. 1 shows a kinetic spray system 10 for use inaccordance with the present invention. The system 10 includes a kineticspray gun 12 which is mounted together with a workpiece 14 within thehollow interior of a vacuum tank 16. The kinetic spray gun 12 isdisposed relative to the workpiece 14 for directing a spray 110 onto theworkpiece 14. The workpiece 14 may be mounted on a workpiecemanipulation device 20 mounted through a wall of the vacuum tank 16 andextending into the interior of the vacuum tank 16.

As shown in the typical system 10 of FIG. 1, the kinetic spray gun 12produces a cold spray for direction onto the workpiece 14 in response toa main gas flow under pressure and a powder gas which carries acomposite powder 100 according to the present invention. The main gasflow is provided to the kinetic spray gun 12 by a main gas line 28 froma first gas supply in the form of a storage container 30. The gas instorage container 30 may be helium, argon, nitrogen or air, for example.The composite powder 100 is provided in a flow of gas by a second gassupply or storage container 32 in combination with a powder feeder 34.The second gas storage container 32 provides a flow of powder gas (forexample, helium, argon, nitrogen or air) through a powder gas line 36extending through the powder feeder 34. The powder feeder 34 feeds thecomposite powder 100 into the flow of gas in the powder gas line 36 forfeeding of the powder to the kinetic spray gun 12.

The gas from the first gas storage container 30 flows through the maingas line 28 to an input end 38 of the kinetic spray gun 12. From theinput end 38, the gas flows through an optional heating coil (not shown)to a spray nozzle 40 at an opposite end of the kinetic spray gun 12 fromthe input end 38. The powder feeder 34 feeds the composite powder 100into the flow of powder gas traveling through the powder gas line 36.The gas from supply 32 and the composite powder 100 mix as the gaspasses through powder feeder 34 to provide a mixture of powder and gas.The ratio of gas from supply 32 and powder 100 can be varied to meetdesired application criteria. As shown in FIG. 1, the powder gas line 36extends through the wall of the vacuum tank 16 to a connecting point 48along the kinetic spray gun 12. Inside the kinetic spray gun 12, thegases and powder are directed through spray nozzle 40 and acceleratedonto the substrate workpiece 14.

The composite powder 100 of the present invention includes a fillermaterial and a solder metal matrix for use in a kinetic spray systemsuch as that described above with respect to FIG. 1. The solder matrixis made up of a low melting point solder material such astin-silver-copper (Sn—Ag—Cu), tin-copper (Sn—Cu), tin-copper-nickel(Sn—Cu—Ni), tin-silver (Sn—Ag), tin-silver-bismuth (Sn—Ag—Bi),tin-bismuth-indium (Sn—Bi—In), tin-gold (Au—Sn), tin-zinc (Sn—Zn),tin-zinc-bismuth (Sn—Zn—Bi), tin-bismuth-silver (Sn—Bi—Ag), tin (Sn),tin-indium (Sn—In), indium (In), indium-silver (In—Ag), or tin-lead(Sn—Pb). The matrix is required to be low in melting temperature, havegood flowability while molten and must also be able to wet the fillerand interface metal. The solder metal matrix can also be an alloy thatdissolves into the filler material. The solder metal matrix can make upbetween about 10 and 90 volume percent of the overall coating, with atypical composition of solder metal matrix being between about 20 and 40volume percent in order to achieve suitable coverage of the fillermaterial in addition to maximizing the benefit of the filler material.

The filler material of the composite powder 100 consists of a soft metalor metal alloy that is high in both thermal and electrical conductivity.The filler material has a melting point that is higher than that of thesolder matrix, and must be able to be wetted by the solder metal matrix.Alternately, the solder metal matrix can dissolve into the filler metalto form a metallurgical bond. The filler material (e.g., a metal orcarbon in graphite, diamond or carbon nanotubes—SWNT) can be composed ofany relatively soft and highly conductive metal or alloy. Metal systemsthat meet these criteria include copper (Cu), gold (Au), nickel (Ni),nickel-gold (Ni—Au), carbon (typically graphite, diamond or carbonnanotubes—SWNT), and silver (Ag) or any alloy combination thereof. Othermetal alloy systems possible are those based on aluminum, molybdenum,nickel or the platinum group metals (PGM's). The filler material canmake up about 10 to 90 volume percent of the coating, with a typicalcomposition being between about 60 and 80 volume percent in order tomaximize the advantages brought by using a metal system with highthermal and electrical conductivity.

The metals for composite powder 100 can be manufactured in a number ofways. In general, metals produced for kinetic spraying are delivered inpowder form, since the kinetic spray apparatus functions by deliveringspherical powder to the part at very high velocities. FIG. 2 shows aprocess flow for a method of producing composite powder blend inaccordance with the present invention. In steps S101 and S103 the basematerials are provided for the solid metal matrix and filler material,respectively. In step S105, the base solid metal matrix material isformed into powder particles. The most common manner of producing thepowder is by gas atomization, as smooth, spherical powders aremanufactured. Other methods of powder formation are, but not limited to,water atomization, or chemical precipitation. The size of the metalmatrix powder particles is less than about 90 microns and greater thanabout 5 microns and must be generally free flowing (e.g., the particlesdo not adhere to one another). Similarly, in step S107, the fillermaterial is formed into powder particles. The powder formation processin step S107 for the filler material may use, but is not required touse, the same powder formation technique as in step S105—any of gasatomization, water atomization, or chemical precipitation may be used.The size of the filler material powder particles is less than about 90microns and greater than about 5 microns and must be generally freeflowing. The gas atomization process can be performed in either an inertatmosphere or else in vacuum. The advantage of using inert atmosphere orvacuum for atomizing is that low oxygen content can be realized in thepowder produced, which becomes important when the deposited coating isto be soldered.

As shown in step S109 of FIG. 2, the two powder components are blendedin the desired ratio prior to spraying using a device such as aV-blender. The two powder components may exhibit different temperaturesand velocities due to differences in density, thermal conductivity anheat capacity as they are propelled from the spray gun nozzle. Dependingon the in-flight characteristics of the solder metal matrix powder andthe filler material powder, the blend ratio is adjusted so that theresulting coating will have the desired volume fractions of theconstituents. In another embodiment, co-injection of two powdercomponents may be used in lieu of a separate blending step.

Another option for manufacturing the powder is to create a compositepowder particle so that production issues involved in blending andfeeding, such as powder separation, are avoided. FIG. 3 provides asketch of a composite powder particle in accordance with the presentinvention. FIG. 3 shows particle 120 that includes a filler material 124surrounded with an outer shell of solder metal matrix 122. The volumeoccupied by the filler material is between about 50 and 90 percent,preferably between about 60 and 80 percent. The size of the compositepowder particles is less than about 90 microns and greater than about 5microns and must be generally free flowing.

FIG. 4 shows a process flow for the method of producing composite powderparticles in accordance with the present invention. In steps S131 andS133, the base materials are provided for the filler material and solidmetal matrix, respectively. In step S135, the filler material is formedinto powder particles. As discussed above with respect to FIG. 2, any ofgas atomization, water atomization, or chemical precipitation processesmay be used to form the filler material powder. To create a usefulcomposite powder particle, in step S137 the solder metal matrix materialis deposited onto the filler material particles using a suitabletechnique. Suitable methods for accomplishing encapsulation in step S137include electrochemical methods, physical vapor deposition (PVD), ormechanical cladding.

Referring generally to FIGS. 1 and 7, kinetic spraying involvesaccelerating composite powder particles 100 towards a substrate (e.g.,workpiece 14) at very high velocities, much greater than the speed ofsound. FIG. 7 provides a process flow for producing a solder coatingonto a substrate. In step S151, the composite powder 100 is provided forthe kinetic spray system. For the system configuration show in FIG. 1,the powder may be supplied as a pre-blended powder or as compositeparticles. In another embodiment, the powder is preheated in step S153.In another embodiment, the solid metal matrix and the filler materialpowder components of composite powder 100 may be fed separately intokinetic spray gun 12 and blended as the particles pass through thekinetic spray gun 12. The composite powder 100 is injected into thekinetic spraying device 12 in step S155. The composite powder 100 isaccelerated to supersonic velocities by injection into a high velocitygas stream. The gas is accelerated in the kinetic spraying device 12 bypressurizing the gas and subsequently expanding it through a properlysized convergent-divergent nozzle 40. The inlet and outlet pressurescombined with the nozzle 40 dimensions and gas flow determine the exitvelocity of the gas. The outlet pressure can be either ambient, orotherwise any pressure lower than ambient. These conditions aredescribed in U.S. Pat. No. 6,759,085, titled “Method and Apparatus forLow Pressure Cold Spraying,” commonly-assigned with the presentinvention.

After the powder 100 is injected into the nozzle, it travels in stepS155, to the substrate 14 in the form of spray 110. A coating is formedby the transfer of the powder's 100 kinetic energy into thermal energyupon impact, forming a mechanical bond with either the substrate 14 orpreviously deposited material. In this manner, it is possible to form avery dense coating without having thermal reactions occur within thepowder in flight such as is the case with other forms of spraydeposition such as plasma spraying, flame spraying or high velocityoxy-fuel (HVOF) spraying. An example of such a solder coating is givenin FIG. 5, showing a schematic of an applied solder coating prior tosoldering in accordance with an embodiment of the present invention. InFIG. 5, a coating 140 is bonded to the substrate 14, with the coatingcontaining densely-packed filler material particles 124 generallysurrounded by the solder metal matrix 122. There may be present in thiscomposite solder coating up to 1 volume percent porosity 126, which willdisappear during the soldering step.

Use of the kinetic spray process provides an advantage over hightemperature thermal spray systems by suppressing thermal reactionsduring flight. This means that composite coatings of metals which wouldnormally react with each other or the environment during spraying can beused and, thus, composite coatings of metals which have very dissimilarmelting points can be achieved. This is the case with co-spraying a lowmelting solder matrix in conjunction with a higher melting point fillermaterial, as in the present invention.

Once the solder coating has been deposited, it can be soldered using asuitable technique such as, SMT (Surface Mount Technology) reflow orwave soldering. The coating of the present invention has advantages withregards to soldering over other solders in that it has both low oxidecontent and high density so that a consistent solder joint is possible.It is also possible to develop diffusion bonding by choosing a fillermaterial and solder metal matrix combination, such as copper and indium,that are soluble in each other. In some cases, it may be possible toachieve joining at temperatures below the melting point of the soldermaterial.

An example of the coating structure of a soldered joint is given in FIG.6, showing a schematic of an applied solder coating 150 after solderingin accordance with an embodiment of the present invention. The coating150 is bonded to the substrate 14, with the coating containingdensely-packed filler material particles 124 generally surrounded by thesolder metal matrix 122. An IC package 200 is joined to the substrate 14by the solder coating 150.

While exemplary embodiments of the invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousinsubstantial variations, changes, and substitutions will now beapparent to those skilled in the art without departing from the scope ofthe invention disclosed herein by the Applicants. Accordingly, it isintended that the invention be limited only by the spirit and scope ofthe claims, as they will be allowed.

1. A kinetic sprayable solder composition for forming a solder joint,the composition comprising: a powder material including a solid metalmatrix material and a filler material; said solid metal matrix materialcomprising one or more of tin-silver-copper (Sn—Ag—Cu), tin-copper(Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag),tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold(Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi),tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium(In), indium-silver (In—Ag), and tin-lead (Sn—Pb); and said fillermaterial comprising one or more of copper (Cu), gold (Au), nickel (Ni),nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum(Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinumgroup metals (PGM's), and their alloys, wherein one of: said fillermaterial has a melting point that is higher than that of said solidmetal matrix material; and said filler material and said solid metalmatrix material each making up between about 10 and 90 volume percent.2. The solder composition of claim 1, wherein the solder composition issprayable onto a substrate via a kinetic spraying apparatus.
 3. Acomposite solder coating formed by spraying the solder composition ofclaim 1 onto a substrate at pressure less than or equal to ambient.
 4. Akinetic sprayable solder composition for forming a solder joint, thecomposition comprising: a powder material including a solid metal matrixmaterial forming an outer shell surrounding a filler material; saidsolid metal matrix material comprising one or more of tin-silver-copper(Sn—Ag—Cu), tin-copper (Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver(Sn—Ag), tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In),tin-gold (Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi),tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium(In), indium-silver (In—Ag), and tin-lead (Sn—Pb); and said fillermaterial comprising one or more of copper (Cu), gold (Au), nickel (Ni),nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum(Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinumgroup metals (PGM's), and their alloys, wherein said filler material hasa melting point that is higher than that of said solid metal matrixmaterial.
 5. The solder composition of claim 4, wherein the soldercomposition is sprayable onto a substrate via a kinetic sprayingapparatus.
 6. A composite solder coating formed by spraying the soldercomposition of claim 4 onto a substrate at pressure less than or equalto ambient.
 7. A kinetic sprayable solder composition for forming asolder joint, the composition comprising: first powder particlescomprising a solid metal matrix material; second powder particlescomprising a filler material; said solid metal matrix materialcomprising one or more of tin-silver-copper (Sn—Ag—Cu), tin-copper(Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag),tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold(Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi),tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium(In), indium-silver (In—Ag), and tin-lead (Sn—Pb); and said fillermaterial comprising one or more of copper (Cu), gold (Au), nickel (Ni),nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum(Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinumgroup metals (PGM's), and their alloys, wherein the solder compositioncomprises a blend of the first and second powder particles, and whereinsaid filler material and said solid metal matrix material each make upbetween about 10 and 90 volume percent.
 8. The solder composition ofclaim 7, wherein the solder composition is sprayable onto a substratevia a kinetic spraying apparatus.
 9. A composite solder coating formedby spraying the solder composition of claim 7 onto a substrate atpressure less than or equal to ambient.
 10. A kinetic sprayable powdercomposition for forming a solder joint, the composition comprising: ametal matrix material and a filler material; said metal matrix materialcomprising one or more of tin-silver-copper (Sn—Ag—Cu), tin-copper(Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag),tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold(Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi),tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium(In), indium-silver (In—Ag), and tin-lead (Sn—Pb); and said fillermaterial comprising one or more of copper (Cu), gold (Au), nickel (Ni),nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum(Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinumgroup metals (PGM's), and their alloys, wherein the powder compositioncomprises one of: a blend of said metal matrix material and said fillermaterial; composite powder particles comprised of said metal matrixmaterial and said filler material; and powder particles each includingsaid metal matrix material forming an outer shell surrounding saidfiller material, and wherein said filler material has a melting pointthat is higher than that of said solid metal matrix material, andwherein the powder composition comprises particles whose size is lessthan about 90 microns and greater than about 5 microns.
 11. The powdercomposition of claim 10, wherein the powder composition is sprayableonto a substrate via a kinetic spraying apparatus.
 12. A compositesolder coating formed by spraying the powder composition of claim 10onto a substrate at pressure less than or equal to ambient.
 13. Thesolder composition of claim 1, wherein the powder material is a blend ofseparate generally free flowing solid metal matrix material particlesand filler material particles.
 14. The solder composition of claim 1,wherein the powder material is a composite powder with particles havingan inside component of the filler material and an outside component ofthe solid metal matrix material and the filler material has higherthermal and electrical conductivity than the solid metal matrixmaterial.
 15. The solder composition of claim 1, wherein the volumepercentage of the solid metal matrix material is between about 20 and 40and the volume percentage of the filler material is between about 60 and80.
 16. The solder composition of claim 1, wherein the powder materialcomprises particles having a size that is less than about 90 microns andgreater than about 5 microns.
 17. The solder composition of claim 4,wherein the solid metal matrix material is a solder metal matrixmaterial and the powder material comprises particles having a size thatis less than about 90 microns and greater than about 5 microns.
 18. Thesolder composition of claim 4, wherein the volume fraction of the solidmetal matrix material in a coating forming said solder joint is betweenabout 10 and 90 percent and the volume fraction of the filler materialin said coating is between about 50 and 90 percent.
 19. The soldercomposition of claim 7, wherein said filler material has a melting pointthat is higher than that of said solid metal matrix material.
 20. Thesolder composition of claim 7, wherein said solid metal matrix materialand said filler material each comprises particles having a size that isless than about 90 microns and greater than about 5 microns.